Flexible corrugated sheet material, method and apparatus



April 11, 1950 c. Q. IVES 2,503,874

' FLEXIBLE CORRUGATED SHEET MATERIAL,

METHOD AND APPARATUS Filed Feb. 27, 1946 3 Sheets-Sheet l April 11, 1950 c. Q. IVES 2,503,874

FLEXIBLE CORRUGATED SHEET MATERIAL,

METHOD AND APPARATUS Filed Feb. 2'7, 1946 3 Sheets-Sheet 2 INVENTOR.

By a :0 04/?! MM whe A ril 11, 1950 c. Q. IVES 2,503,874

FLEXIBLE CORRUGATED SHEET MATERIAL,

METHOD AND APPARATUS s-Sheet Filed Feb. 27, 1946 INVENTOR. QM; a? 45/ Patented Apr. 11, 1950 FLEXIBLE CORRUGATED SHEET MATERIAL, METHOD AND APPARATUS Charles o. Ives, Reading, Mass. Application February 27, 1946, Serial No. 650,039

22 Claims. 1

This invention relates to corrugated sheet material and more particularly to flexible corrugated paper and to methods and the same.

Main objects of the invention include production of an improved flexible corrugated sheet material, of paper or they like, and the provision of apparatus and methods for fabricating the same;

Normal corrugated paper constituted of a reinforcing plane ply faced with a corrugated ply adhesively or otherwise secured to the reinforcing ply has flexibility in the direction of the flutes but in folding such paper in a cross direction one meets the resistance of the corrugations which must be crushed to make the fold. When the material is used for wrapping purposes, wherein the corrugated paper is folded about a .cornerof a box or other article, crushing and breakdown of the corrugations along any transverse fold de-v stroys the cushion effect of the material at the folded corner, where it is most needed, thus failing to achieve one of the very purposes for which the material is used. Furthermore, inability to make neat straight-line transverse folds detracts from appearance and deprives the package of the greater protection of snug wrapping.

It has been proposed heretofore to render corrugated paper flexible as for example by breaking down or crushing the corrugations at spaced intervals. Such a flexible corrugated paper is shown and described in my prior patent, Reissue No. 20,034. Commercial embodiments of this invention have, however, had the disadvantage that the formation of the indentations in the flutes has always tended to destroy to a greater or less degree the normal contour of all the flutes throughout the whole area of the paper. Patent to McKeage No. 2,253,718, issued August 26, 1941, to the owner of my prior Reissue Patent No. 20,034 recognized this undesirable distortion in the patented construction resulting from the tendency toward crushing or wrinkling of the plies" which cannot altogether be overcome.

In accordance with the present invention, flattening, crushing or other distortion of the flutes is wholly avoided, yet the sheet material has, in addition to usual flexibility along fold lines parallel to the corrugations, substantially equal flexibility along fold lines perpendicular to the corrugations andgood flexibility along fold lines non-parallel and non-perpendicular to the corrugations, plus certain other advantages including straight-line transverse folds and snug flt at corners with good cushioning protection.

Corrugated sheet material of this invention in apparatus for making 2 conventional corrugated paper, a reinforcing plane ply and an overlying corrugated ply adhesively or otherwise amxed to the reinforcing ply. Inasmuch as the invention is particularly useful in the fabrication of flexible corrugated paper wrapping, embodiments of the invention shown in the drawings, and the ensuing description, will flute sections.

refer particularly to the use of paper as the material of the plies, although it should be understood that any other suitable flexible sheet material may be substituted as the reinforcing ply, andas the corrugating being corrugated.

- The flexible material of this invention departs ply so long as it is capable of in structure from conventional corrugated paper and previous flexible corrugated paper in that.

the corrugations vor flutes, or certain sections thereof, are interrupted or terminated at spaced intervals, with the top and side walls of. the flutes terminating in the ,directionof the crest lines at out edges, so cut as to form transecting voids between the cut edges of the adjacent truncated Despite the presence of these voids, the flute sections, though truncated, are undistorted, so that the finished article possesses all the benefits derived from normal flute shape,

including good resistance against shock.

The above and other characteristics and advantages of products of my invention will be more fully explained and described in connection with a description of the accompanying drawings, in which Fig. 1 is a fragmentary plan view of corrugated sheet material having the structure of this invention;

Fig. 2 is a section taken along the line 2-2 of Fig. 1;

Fig. 3 is a section taken along the line 3-3 of Fig. 1;

Fig. 4 is an enlarged detail cross section taken I along the line 4-4 of Fig. l;

its preferred form comprises, as in the case of Fig. 5 is a cross-sectional view of the material when folded as along the line A-A of Fig. 1 around an article to be packed;

Fig. 6 is a fragmentary perspective view of the material of Fig. 1; I I

Fig. 7 is a perspective view partially broken away of the material of Fig. 1 when folded as along the line BB of Fig. 1;

Fig. 8 is an isometric view of a tubular package formed from the material'of'this invention.

Fig. 9 is a diagrammatic illustration of a preferred form of apparatus useful in the fabrication of material of this invention;

Fig. 10 is a. front elevation of the apparatus of Fig. 9, broken away to show extent;

Fig. 11 is a detail illustrating the operation of the apparatus of Figs. 9 and in the production of material of this invention;

Fig. 12 is a diagrammatic illustration of a different form of apparatus for fabricating flexible corrugated material of this invention;

Fig. 13 is a plan view of sheet material, broken away to show extent, indicating the operations performed by the apparatus of Fig. 12;

Fig. 14 is a sectional detail indicating a modification of the apparatus shown in Fig. 9; and

Fig. is a partial plane view of certain of the structure of the modification shown in Fig. 14.

Figs. 1, 2 and 3 show a flexible sheet material having the structure of this invention, which may be created by processing a sheet of normal single face" corrugated paper. The material includes a reinforcing ply l0 and a corrugated ply 12 adhesively or otherwise amxed to the reinforcing ply ID in the conventional manner utilized in the formation of single face corrugated paper. As shown in Figs. 1 and 2. however, the material of this invention is distinguished from conventional corrugated paper in that the corrugations of the corrugated ply l2 are interrupted at spaced intervals as illustrated in Fig. 2 by the removal of portions of the material of the corrugated ply 12 in a manner, for example, as hereinafter described, to leave lines of open-ended truncated flutes l3 separated in the direction of their crest lines by voids M. In the form shown in Fig. 1, these interruptions or voids l4 occur at uniformly spaced intervals along each corrugation throughout the sheet and are aligned in rows extending substantially normal to the directions of the corrugations. The sheet then is characterized by rows of longitudinally and laterally aligned spaced truncated flutes extending over the entire face of the reinforcing ply to present what I refer to as a knob-like surface, although, for purposes to be hereinafter described, the interruptions or voids It may be confined to any desired area of the sheet.

In the preferred case and as shown particularly in Fig. 2, the truncating edges IG defining each void or interruption M are straight and lie in planes disposed at an angle of substantially 90 to each other and at angles of substantially 45 to the plane of the reinforcing plane ply 10. Also, as shown in Fig. 2, the line of intersection l8 of the truncating edges defining each void lies substantially at or above the plane: of the top surface of the reinforcing ply ID in the areas intervening the lines of corrugations. In other words, the interruptions or voids l4 extend downwardly through the corrugations to a limited extent only so that those portions of the corrugated ply I! which bear on their undersurfaces the adhesive afiixing thecorrugated and reinforcing plies together, will not be destroyed, and the integrity of the reinforcing ply will be preserved to maintain strength. l

The interruptions or voids can be formed in the material of the corrugating ply either after or before corrugating and/pr adhesively affixing the corrugating ply to the reinforcing ply. Thus.

conventional finished corrugated sheet materialmay be fed through cutting apparatus designed to transect the corrugations in the desired manner at the desired intervals. I have found that highly acceptable cuts can be made with abrasive tools, as for example abrasive cutting wheels.

Such wheels may be gauged on an arbor in ap- 24 mounted along the arbor 20 on centers correlated with the transverse distance between the voids or interruptions desired to be formed in the particular material being operated upon. For this purpose spacers 25 may be mounted on the arbor 20 between the cutting wheels 24. The shape of the working periphery of the cutting wheels is such as to impart to the material the particular shape of void desired. Thus, for example, in the case of the V-shaped right-angled void illustrated in the preferred form of material shown in Figs. 1 to 3, inclusive, the cutting wheels may have working peripheries shaped as shown in Fig. 11, presenting a male contour corresponding to the female contour of the voids.

The frame 22 carries an anvil roll 30, mounted under the arbor 20 in vertically adjustable journals carried by the frame 22. This roll provides a supporting surface adapted to present the material to be cut to the cutting wheeis in such manner as to' effect a proper depth of cut. Vertical adjustment of the anvil roll 30 may be effected by the incorporation of any suitable adjusting mechanism, exemplified in the drawings by the hand adjustment wheels 28.

The apparatus also includes a suitable intake guide roll 34 and drive roll 35, each of which may have a corrugated surface conforming with the contour of the corrugated sheet material being operated upon or may be provided with other surface suitable for carrying the material without damage through the cutting apparatus.

As shown in Fig. 9, the corrugated material is fed through the apparatus with its corrugated surface upward and in a direction normal to the direction of the corrugations so that as the material passes over the anvil roll 30 the cutting wheels, which turn in a direction opposite to the direction of advance of the material, cut across the corrugations to a depth depending upon the adjustment of the anvil roll 30, and form, depending upon the number and spacing of the cutting wheels, simultaneously in each corrugation interruptions orvoids similar to or exactly the same as those shown in Figs. 1, 2 and 3.

Where this apparatus is designed to operate on sheet material of considerable width, for example '72 inches more or less. the accuracy of the cut is dependent upon the precision of each tool in the gang. Accordingly, inaccuracies of cut may be encountered in the larger widths when the span of the cutting wheel arbor is coextensive with the width of material-being operated upon. In such cases the cutting wheels, instead of being mounted on a single arbor as shown in Figs. 9 and 10, may be grouped, as shown in Figs. 14 and 15, on separate arbors 36 journalled on alternate sides of a heavy transverse beam 31 and driven by suitable belting and pulleys (not shown). The wheels of certain arbors 36 are thus spaced laterally and longitudinally with respect to the anvil roll surface 30 to operate in succession on different lanes of the material, the material being simultaneously out in certain lanes -by-the cutting wheels on advance aligned arbors 36 and then being cut in different lanes, intervening the cut lanes, by the cutting wheels on rear aligned arbors 38.

While the desired cutting may be effected by the use of a variety of cutting tools either stationary, reciprocating or rotating, the use of abrasive cuttingwheels has been found to have particular advantages in -thecase of paper, in that, where the cutting wheels are sufliciently coarse and operateat sufficient peripheral speeds to prevent tearing or burning of the cormgated ply, they act to shred some of the material, which is being removed in the formation of each void, into a fibrous mass, some of which is pushed into the spaces beneath the arches of the truncated flutes l3. The presence of this material, as roughly indicated by the reference 38. inFigs. 3 and'4, in the finished product adds to the cushion value of the truncatedflutes by providing,'as it were, a soft resilient filler therefor.

. Thematerial of Fig. 1 is particularly adapted for wrapping use involving folding r bending of the material around corners, as it forms straight-line 90 folds transverse to the lines of corrugations without loss of any cushioning ac-v tion of the corrugations on each side of and at the corner, and provides, by reason of the shape of the voids, a wholly novel miter-joint having equal strength with the rest of the sheet and resisting in particular crushing of the corner or folding beyond the desired 90 fold. Where the shape of the interruptions or voids is that shown in Fig. 1 with the cut walls of the corrugations meeting at each void at an angle of substantially 90, the relation of the portions of the structure is that shown in Fig. 5, when the material is folded along a line such as AA of Fig. 1 about an article 39 to be packed. As there shown, folding brings the terminating wall of one truncated flute 13 into abutting relationship with the cut wall of an adjacent truncated flute IS in the same corrugation line and this relationship is repeated throughout the extent of the fold line. This abutting relationship forms in effect uninterrupted corrugations extending around the corner to furnish protection at the fold substantially that of full corrugations. Corner structure of this character is wholly unobtainable in corrugated paper processed on scorers or creasers, such machines so crushing the corrugations in the area of the fold as to destroy any corner protection in so far as corrugations are concerned.

Where other than 90 folds are contemplated, the angular relationship of the truncating edges may be varied to secure a miter-joint for any contemplated angle of fold, fo example 30, 60, 120 or 150", thus attaining the strength of the butt corner in folds other than 90 folds.

In Fig.8, the benefits of the corner fold shown in Fig. 5 are illustrated in the production of a tubular package. In this instance, it suflices to space the interruptions or voids in such manner that they are presented only along those portions of the material coinciding with the four corners of the finished package. This of course may be accomplished by spacing the wheels on the arbor in such manner as to cut the corrugations only along these particular lines and will involve considerable saving in those cases where the sheet material is to be used in the production of large numbers of identical packages. The package of Fig. 8 is shown fastened by a tape 40 at one corner. In this case the sheet material before folding will have half voids at the edges resulting from slitting the sheet, after formation of the voids, down two lines of voids separated by three lines of voids, as will be understood. If desired, the ends of the sheet material may be at other than a corner and taped, lapped or otherwise fasthe particular spacing relation as just defined,

truncated flutes lying along alternate lines of corrugations in the overfolded layer can fall into and along the lines of the voids in the corrugations of the underlying layer in one direction, and truncated flutes lying alongalternate lines of corrugations in' the underlying layer extend upwardly into and along the lines of voids in the overfolded layer in the other direction. In that event, truncated flutes lying along intervening lines of corrugations in both layers will impinge directly upon each other. Where the faces of the folded material have this meshed relationship, as shown in Fig. 7, truncated flutes lying along alternate lines of corrugations in both layers will maintain the original shape and contour of their unfolded state and therefore provide in the folded state the same cushioning effect that they provide in the unfolded state without materially increasing the dual thickness over the unfolded thickness. These characteristics are highly desirable in the case of a threedimensional' corner fold, wherein the two-dimensional fold will have the straight line miter-joint,

as shown in Fig. 5, and the fold over the surface lying in the thrd dimension will incorporate the angle fold shown in Fig. 7, and have the benefitsthereof as just described to form a threedimensional corner covering of improved appearance, strength and cushioning protection without undue'bulk.

For the purpose of clarity with reference to the spacing of the voids, examples may be given as follows: v

In the case of A" flute the l nes of flutes or corrugations are usually spaced apart a distance interruption should be sufllclent to permit lateral relative motion between adjacent truncated flutes in the same line of corrugation to provide the flexibility which is the object of this invention. In general, the dimension of the void along the crest line of the corrugation should not be less than 1 5 of an inch. Otherwise in folding the material the corrugations are liable to crush and break down in the same manner as in normal corrugated paper. With the V- .shaped cut indicated in Fig. 2, the dimension of the voids along the crest lines may approximate of an inch and of the individual truncated or segmentary flutes along the crest lines approximate of an inch where, as is usual in the case of A flute, the height of the flutes is approximately 3%, plus or minus usual commercial tolerance.

In the case of another typical commercial single face corrugated paper, 1. e. B flute, nor- 5 mal spacing betweenthe corrugations is of an 7. inch, plus or minus usual commercial tolerance, in which case the corresponding dimension .171! should be approximately of an inch. It will be understood that in the case of 28" flute. C flute or mongrel flutes, the spacing of the cutting wheels in the apparatus of Figs. 9, 10 and .11 should be modified in order to provide the particular dimensional relationships just described in the production of the preferred forms of corrugated surfaces of the invention. In the case of any of these sheets, the individual distinct ridge-like truncated flutes forming the knob-like surface of sheets of this invention have, in the preferred form of structure wherein the cuts are made at an angle to the plane of the reinforc'ng ply, the inherently strong trapezoidal structure often sought in engineering design.

In so far as creation of the actual structure of sheets of this invention is concerned, the necessary removal of material from the corrugated sheet may be accomplished by any suitable cutting means including stationary, rec'procating, or rotating cutters such as milling cutters or knives. However, for reasons hereinbefore recited, the use of abrasive cutting wheels have afforded certain advantages, such as the filling of the segmented flutes as hereinbefore described, not as effectively produced in the case of milling tools.

As previously indicated, material of this invention may also be fabricated by creating the interruptions or voids in the material of the corrugating ply before the corrugating ply is corrugated. Apparatus for fabricating corrugated sheet material in this manner is illustrated in Fig. 12 where a corrugating ply i2 is fed from a suitable source of supply such as roll 4| to and through a conventional corrugating machine as illustrated having a pair of opposed corrugating rolls 42 and 43. After the ply I2- is corrugated it passes over a transfer roll 44 which coats the tops of the flutes on the underside with an adhesive picked up from a glue pot 46 in the conventional manner. A supply of reinforcing ply l such as contained on a roll 48 is fed around a roll 45 into contact with the previously coated flute portions of corrugating ply l2. The assembled corrugated paper is then fed to a suitable rewinder mechanism 50. In order to secure the flexible structure of this invention, the apparatus is provided, in advance of the corrugating rol's 42 and 43, with a pair of cutting dies 54 and 55. These cutting dies are adapted to puncture successive transverse rows of apertures in the corrugating ply 12, as it is fed to corrugating rolls 42 and 43. In order to form a structure having the preferred spacing of the material shown in Fig. 1 and previously described, the centers of the cutters are spaced laterally on the cutting roll die 54 a distance substantially equal to twice the distance between the crest lines of the corrugations of the corrugating rolls 42 and 4 3; and are spaced apart circumferentially of the die roll 54 a distance substantially equal to the surface dimension between the crest lines of the corrugations of the corrugating rolls so that, after the ply i2 is corrugated by the corrugating rolls 42 and 43, the distance between the center lines of lateral rows of apertures is substantially equal to the distance between the crest lines of the corrugations on the corrugating rolls 42 and 43. It will be understood that, in order to have the voids or apertures l4 formed in the material at that portion thereof which after- 8 wards lies along the fluting lines imparted by the corrugating rolls 42 and 42,.the rolls 54 and BI must be properly spaced from and the cutters operated in timed relation with the corrugating rolls 42 and 43. In this method of fabrication the size of the apertures should preferably be such that the distance between the'apertures longitudinally of the ply l2 issuflicient to secure adhesion of the corrugating ply II to the reinforcing ply ID in the areas lying longitudinally between the apertures l4.- However, this is not essential, as the structure of the invention will be secured even when the dies 54', 55 act to sever the material into a series of longitudinal strips which are afterwards affixed in closely spaced relation to the ply "I in the corrugating machine.

By the actual removal of portions of the walls of the flutes, novel variegated eflects may be secured where the materials of the reinforcing and corrugating plies are contrasting. for example in color. Such material has novel decorative uses.

While in the description of the preferred product as hereinabove given, reference has been madeuniformly to the use of paper as the reinforcing and corrugating ply components, it will be understood that the invention is adapted for use in forming any flexible corrugated sheet material having flexible plies of sheet material including, but not limited to, unwoven or woven fibrous or non-fibrous material such as paper, cloth or plastics. Among these materials are non-resilient materials which do not retain indentures or creases and which are therefore not susceptible to heretofore proposed methods of rendering corrugated sheet materials flexible.

I claim:

l. Corrugated sheet material having a flexible reinforcing ply and a corrugated ply adhesively secured thereto, the flutes of the corrugated ply being interrupted in at least some areas of the sheet along a plurality of substantially parallel lines disposed at an angle of substantially to the lines of corrugations, with the top and side walls of the flutes terminating at the interruptions along cut edges defining voids in the corrugated surface and the distance between at least some of said parallel lines being substantially equal to twice the distance between the crest lines of the corrugations.

2. The method of fabricating flexible corrugated sheet material which includes the step of removing portions of the material of the corrugating ply to form a plurality of voids spaced along the portions of the corrugating ply which lie along the flute lines of the corrugated sheet.

3. The method of fabricating flexible corrugated sheet material which includes the step of simultaneously removing portions of the material of the corrugating ply to form a plurality of V- shaped voids spaced along that portion of the corrugating ply which lies along a single flute line of the corrugated sheet.

4. The method of fabricating flexible corrugated sheet material which includes the step of removing portions of the material of the corrugating ply to interrupt the continuity of the walls of the flutes of the corrugated sheet along a plurality of substantially parallel lines intersecting the flute lines and space the flutes apart at the interruptions a distance of not less than of an inch along the crest line.

5. The method of fabricating flexible corrugated sheet material which includes the step of removing portions of the material ofthe corru-.

9 gating ply to interrupt the continuity of the walls of the flutes of the corrugated sheet along a plurality of substantially parallel lines intersecting the flute lines and spaced apart a distance substantally equal to twice the distance between the crest lines of the flutes of the corrugatedsheet.

6. The method of processing corrugated sheet material having a corrugated ply presenting flutes, to improve the flexibility of the material in directions angularly related to the direction of the flutes, comprising removing portions of the material of the corrugated ply to a width of not less than 1*; of an inch to form voids transecting the corrugations along a plurality of substantially parallel lines.

'7. The method of processing corrugated sheet material having a corrugated ply presenting flutes to improve the flexibility of the material in directions angularly related to the direction of the flutes, comprising cutting the corrugated ply to remove portions of the material thereof to a width of not less than 1 of an inch and form voids in the walls of the flutes.

8. The method of processing corrugated sheet material having a corrugated ply presenting flutes, to improve the flexibility of the material in directions angularly related to the direction of the flutes, comprising simultaneously cutting the corrugated ply along a plurality of substantially parallel cutting paths intersecting the corrugations to remove portions of the material thereof to a width of not less than of an inch and form voids transecting the corrugations.

9. The method of processing corrugated sheet material having a corrugated ply presenting flutes to improve the flexibility of the material in directons angularly related to the direction of the flutes, comprising removing a portion of the material of the corrugated ply to form voids in the walls of the flutes and displacing at least a portion of the removed material to positions beneath the arches of the flutes.

10. In the fabrication of flexible corrugated sheet material, the steps which comprise forming apertures in the material of the corrugating ply, and then corrugating said ply and adhesively securing the corrugated ply to a reinforcing ply.

11. In the fabrication of flexible corrugated sheet material, the steps which comprise forming rows of apertures in the material of the corrugating ply and then forming flutes in said ply having their crest lines substantially aligned with the center lines of the rows of apertures and adhesively securing the corrugated ply to a reinforcs ply.

12. In the fabrication of flexible corrugated sheet material, the steps which comprise forming rows of longitudinally and laterally aligned apertures in the material of the corrugating ply and then forming flutes in said ply with the crest lines of the flutes substantially aligned with the center lines of the lateral rows of apertures and separated longitudinally a distance substantially equal to one-half the distance between the longitudinal rows of apertures, and adhesively securing the corrugated ply to a reinforcing ply.

13. Apparatus of the character described comprising a supporting surface, a plurality of circular abrading tools mounted in spaced relation to said surface and means for advancing a sheet of corrugated paper in a direction transverse to the direction of the flutes thereof between said supporting surface and said abrading tools to cut the flute walls transversely along a plurality of substantially parallel cutting paths.

14. Apparatus of the character described comprising a frame, a; supporting surface adiustably mounted on said frame for movement relative thereto, a plurality of cutting tools mounted on said frame in spaced relation to said surface and means for advancing a sheet of corrugated paper in a direction'transverse to the flutes thereof between said supporting surface and said cutting tools to out the flute walls transversely.

15. Apparatus of the character described comprising a frame, a supporting surface adjustably mounted on said frame for movement relative thereto, a plurality of rotary abrasive wheels co-axially mounted on said frame in spaced relation to said surface and means for advancing a sheet of corrugated paper in a direction transverse to the flutes thereof between said supporting surface and said abrasive wheels to cut the flute walls transversely along a plurality of substantially parallel cutting paths. 7

16. Apparatus of the character described comprising a supporting surface, cutters mounted in spaced relation to said supporting surface, one

. cutter being laterally and longitudinally spaced with respect to said surface from another cutter, and means for advancing a sheet of corrugated paper in a direction transverse to the direction of the flutes thereof between said supporting surface and said cutters to cut the walls of the flutes transversely first with said one cutter along one cutting path and then with the said other cutter along another cutting path.

17. In apparatus for fabricating corrugated sheet material having corrugating rolls and means for adhesively securing a corrugating ply to a reinforcing ply, cutters in advance of the corrugat-- ing rolls adapted to form apertures in the corrugating ply as it is fed to the corrugating rolls.

18. In apparatus for fabricating corrugated sheet material having corrugating rolls and means for adhesively securing a corrugating m to a reinforcing ply, cutters in advance of th corrugating rolls adapted to form apertures in the corrugating ply as it is fed to said corrugating rolls, the cutters being so spaced laterally that the centers of the apertures which they out are spaced laterally of the corrugating ply a distance substantially equal to twice the distance between the crest lines of the corrugations of the corrugating rolls.

19. In apparatus for fabricating corrugated sheet material having corrugating rolls and means for adhesively securing a corrugating ply to a reinforcing ply, cutters in advance of the corrugating rolls adapted to form apertures in the corrugating ply as it is fed to said corrugating rolls and means for operating said cutters in timed relation to the advance of said sheet to form apertures in said sheet spaced longitudinally of the advancing ply a distance substantially equa1 to the surface dimension between the crest lines of the corrugating rolls.

20. In apparatus for fabricating corrugated sheet material having corrugating rolls and means for adhesively securing a corrugating ply to a reinforcing ply, cutters in advance of the corrugating rolls adapted to form apertures in the corrugating ply as it is fed to said corrugating rolls, the cutters being so spaced laterally of the apparatus that the centers of th apertures which they out are spaced laterally 0f the corrugating ply a distance substantially equal to twice the distance between the crest lines of the corrugations of the corrugating rolls and means for operating said cutters in timed relation to the advance of said sheet to form apertures in said sheet spaced longitudinally of the advancing ply a, distance substantially equal to the surfac dimension between the crest lines of the corrugations of the corrugating rolls.

21. Flexible corrugated sheet material having a flexible re-eniorcing ply and a corrugated ply adhesively secured thereto, the flutes of the corrugated ply being interrupted in, at least some areas of the sheet along a series of substantially parallel lines perpendicularly intersecting the corrugations, with the top and side walls 01 the flutes terminating at the interruptions along cut edges defining voids in the corrugated surface between laterally aligned spaced truncated flute sections a forming a knob-like surface on said sheet material.

22. Flexible corrugated sheet material as claimed in claim 21, wherein said parallel lines are equidistantly spaced and said truncated flute sections in said areas are of identical size and shape.

CHARLES Q. IVES.

l2 nnrnaancas crrEn The following references are of record in the ille of this patent:

UNITED STATES PA'I'ENTS Number Name Date 463,300 Averell Nov. 17, 1891 1,173,575 Holly Feb. 29, 1916 1,782,399 Amy Nov. 25, 1930 1,875,188 Williams Aug. 30, 1932 1,929,117 Leyner et al Oct. 3, 1933 1,944,282 Snyder Jan. 23, 1934 1,970,746 Grayson et a1 Aug. 21, 1934 2,142,548 Anderson Jan. 3, 1939 2,154,940 Ives Apr. 18, 1939 2,240,256 Elmendorf Apr. 29, 1941 FOREIGN PATENTS Number Country Date 618,066 Germany Aug. 31, 1935 

